Graphene is an allotrope of carbon in which carbon atoms are densely packed in a hexagonal pattern as a two-dimensional monolayer. Because of its impressive physical properties, including high mechanical strength, high intrinsic carrier mobility at room temperature, high thermal conductivity, unique optical properties, etc., graphene has attracted considerable interest in the past several years. Potential applications include use in nanoelectronics, sensors, nanocomposites, supercapacitors, and hydrogen storage.
A number of methods have been devised for producing graphene, with varying degrees of success. Examples include exfoliation of monolayers from graphite—typically requiring multiple exfoliation steps—chemical methods, chemical vapor deposition, laser techniques, supersonic spray techniques, microwave oxidation, and other methodologies. A detonation process is described in U.S. Pat. No. 9,440,857. Production of graphite oxide using the Hummers' method, followed by chemical reduction to form graphene, is environmentally unfriendly, time-consuming, and expensive. Indeed, most production methodologies devised to date suffer from various disadvantages, including high cost, the need for expensive or even exotic equipment, the need for multiple steps and the use of hazardous reagents, unsuitability for commercial production, etc. What is needed are improved methods and apparatus for making graphene utilizing off-the shelf components requiring little modification while yielding low-defect graphene monolayers in commercial quantities.